Gautama Shakaymuni Buddha was born as a prince in the city of Lumbini of
Nepal, north of India, probably in 563 BC. There is no strong evidence to show
which day was his birthday.

At the age of 16, he had a marriage arrangement with his cousin
by his father, king of Shakya. At the age of 29, he left his palace to find the solution for
the pain of birth, oldness, disease and death. He devoted himself to spiritual
pursuits and Yoga practices. He failed by abstaining from taking food by
practicing self-mortification and asceticism. Later, he changed his method and accepted a little milk and rice pudding
from a village girl. At the age of 35, he attained Enlightenment
after 49-day meditation. After 45-year spreading his doctrine, he entered the
Parinirvana (Nirvana - Complete Silent - Death) in 483 BC.

All Buddhism Sutra (Bible) were written more than one hundred
year after Buddha's Parinirvana. Those manuscript of sutra has vanished. Many
people deny that the sutra was spoken by the Buddha. A Chinese Buddhist monk,
Faxian, who traveled to India and Sri Lanka to bring Buddhist scriptures
back to China during A.D. 399-412. The sutra were translated into Chinese from Pali
language, which is a literary language of the Prakrit language family.
Pali language was commonly used at the time of Buddha. From those translated
sutra,
Chinese estimated the time of Buddha's Birthday, Buddha's Enlightenment and Buddha's Nirvana
based on the lunar calendar. Ancient India used the Hindu Calendar, which is
similar to Chinese lunar calendar. The following days of Buddha's festival are
celebrated each year today in all Chinese Buddhist temples. Asia countries
imported Chinese Buddhism follow the same dates.

The biggest festival is the Buddha's Birthday. Many counties, which are uncertain the time of Buddha's
birthday, celebrates on the full moon day in May using Gregorian calendar, which is close to 15th day of 4th Chinese lunar month.
Because a solar month is longer than a lunar month. May might contains two full
moon days, such as May 2nd and May 31st in 1988. Also, in USA time zones, May
2007 contains two full moon days on May 2nd and May 31st.